Prefabworld Bali's over water built in-house developed building system
A. P iling depth
Our company has developed a special system and technique to have our models safely built over water, either in lakes or coastal waters. Our senior in-house Civil/Hydraulic and Geotechnical engineer with 50 years of International experience under his belt may help and advise you on the required piling, piling depth and superstructure. In order to safely determine the pile capacities one need to take into account the pile's end bearing capacity + negative or positive friction along the pile shaft. This will define the safe pile driving depth. Waves have minor influence on piles, however, it needs to be investigated if wave run up caused by cyclones need a special superstructure. Our company would be happy to prepare a quotation for the engineering works for your over water project, even when you will not order one of our units. Pile structures can be made from either concrete, steel or wood. the latter being the cheapest.
You may also request us to prepare a free of charge ballpark volume estimate for your over water project. To this end we need data such as the seabed subsoil configuration (sand, clay, coral, rock. or a combination thereof), the water depth and the type of the house that will sit on the pile structure. We can only provide a general Bill of Quantities (volume estimate). Unfortunataly we are unable to make a cost estimate since we do not know the prices of materials (piles, concrete, etc) in your area. You need to inquire the prices by yourself based on our BOQ as to acquire a ballpark cost figure.
B. Timber piles
Properly employed timber marine piles are a long term, low cost, environmentally sustainable solution. They do not corrode and proper treatment protects them from environmental degrade mechanisms such as marine borers and rot. They do not require expensive cathodic protection systems or expensive coating systems to provide them with adequate service life, but they will benefit from wrap or a PVC tube encasement between the mud line and the high tide mark. If this is done the piles will outlast their counterparts with low initial cost, very low ongoing maintenance costs and wil last for > 50 years.
Piles below the mud line will not decay or be attacked by marine borers. Above the mud line and below the high tide mark (splash zone) they are susceptible to various levels of marine borer attack. This is generally classified in various standards as high hazard in salt water (coastal and some salt water rivers). In these waters we recommend a treat with a special wrap. Such treatment protects the timber from all kind or marine borers such as the most dangerous shipworm (Toredo, Bankia), the less dangerous gribble, piddocks, pill-bucks, and more.
C. Concrete and steel pipe piles
Nowadays most of the piling designs for over water structures define either concrete piles or steel pipe piles (open or closed at the bottom), connected at the top by concrete capping beams. Such structures will not be affected by marine borers and/or rot, however, steel pipe piles need to be protected by concrete collars extending from the bottom of the capping beams to below the splash zone as to protect the piles from corrosion. In addition often a cathodic protection system is added . The surfaces of the submerged steel pipe piles are often extra protected with a coaltar eppxy resin treatment.
Concrete exposed to seawater is wetted by a solution of salts, principally sodium chloride and magnesium sulfate. Damage to concrete, if it occurss, usually results from failure to use good practices in concrete construction. Magnesium sulfate may attack most, if not all, of the constituents of hardened portland cement paste, especially the aluminate constituent; chlorides may promote corrosion of steel; alkalies may participate in alkali-aggregate reaction. Thus, concrete exposed to seawater should be made with cement of controlled aluminate content and with nonreactive aggregate, embedded steel should be well covered (higher than normal practice) by concrete of low permeability, and good construction practices should be followed.
NOTE: In the event that you will not order an over water unit from us but only need the design for the over water substructure + piles, let us know via our contact form. Our senior civil/hydraulic engineer would be happy to help and advise. Click <here> for his credentials.